Objectives for Nervous System Unit

Organization of the Nervous System

Define central nervous system and peripheral nervous system and list the major parts of each.

 Central nervous system (CNS)◦ Brain◦ Spinal cord

Peripheral nervous system (PNS)◦ Nerves outside the brain and spinal cord

Spinal nerves- 31 pairs Cranial nerves- 12 pairs

Nervous Tissue: Structure and Function

State the function of neurons and neuroglia.

Neurons : transmit messages (nerve impulses) from one part of the body to another.

Neuroglia

1. supporting cells act as phaogcytes 2. protect and myelinate 3. act as a selective barrier between the capillary blood supply and neurons

Describe the general structure of a neuron, and name its important anatomical regions.

◦◦ Major regions of neurons

Cell body —nucleus and metabolic center of the cell Processes —fibers that extend from the cell body

List the two major functional properties of neurons.

Irritability and conductivty

Classify neurons according to structure and function.

Function

Sensory (afferent) neurons Carry impulses from the sensory receptors to the CNS

Motor (efferent) neurons Carry impulses from the central nervous system to viscera,

muscles, or glands Interneurons (association neurons)

Found in neural pathways in the central nervous system Connect sensory and motor neurons

Structure1. Multipolar neuron have several processes extending from its cell body

All motor neurons and interneurons!2. Bipolar neurons—one axon and one dendriteFound in eyes and nose as receptor cells3. Unipolar neurons—have a short single process leaving the cell body

Sensory neurons found in PNS ganglia

Describe the events that lead to the generation of a nerve impulse and its conduction from one neuron to another.

Define reflex arc and list its elements.

•  1. Reflex—rapid, predictable, and involuntary response to a stimulus

 

Stimulus at distalend of neuron

Skin Spinal cord(in cross section)

Interneuron

Receptor

Effector

Sensory neuron

Motor neuronIntegrationcenter

(a)

 

Central Nervous System

Identify and indicate the functions of the major regions of the cerebral hemispheres, diencephalon, brain stem, and cerebellum on a human brain model or diagram.

1. Cerebral hemispheres (cerebrum)2. Diencephalon3. Brain stem

Medulla oblongata- most important autonomic center of the brain & contains autonomic centers regulating heart rate, respiration, and other visceral activities.

4. Cerebellum- coordinates complex muscular movements

Name the three meningeal layers and state their functions. Protection of the Central Nervous System

1. Dura mater-outermost layer; tough fibrous connective tissue,

2. Arachnoid layer

3. Pia mater-innermost vascular layer covering the brain; follows every convolution

Discuss the formation and function of cerebrospinal fluid and the blood-brain barrier. Protection of the Central Nervous System

cerebrospinal fluid

choroid plexus- structure that forms the cerebrospinal fluid Forms a watery cushion to protect the brain

blood-brain barrier

Includes the least permeable capillaries of the body Excludes many potentially harmful substances

List two important functions of the spinal cord.

1. Conduction pathway

2. Reflex center

Describe spinal cord structure.

 

 

Peripheral Nervous System

Describe the general structure of a nerve.

Identify the cranial nerves by number and by name, and list the major functions of each.

I Olfactory nerve—sensory for smell

II Optic nerve—sensory for vision

Endoneurium surrounds each fiber

Groups of fibers are bound into fascicles by perineurium

Fascicles are bound together by epineurium

The connective tissue wrappings help insulate the nerve.

III Oculomotor nerve—motor fibers to eye muscles

IV Trochlear—motor fiber to eye muscles

V Trigeminal nerve—sensory for the face; motor fibers to chewing muscles

VI Abducens nerve—motor fibers to eye muscles

VII Facial nerve—sensory for taste; motor fibers to the face

VIII Vestibulocochlear nerve—sensory for balance and hearing

IX Glossopharyngeal nerve—sensory for taste; motor fibers to the pharynx

X Vagus nerves—sensory and motor fibers for pharynx, larynx, and viscera

XI Accessory nerve—motor fibers to neck and upper back

XII Hypoglossal nerve—motor fibers to tongue

Describe the origin and fiber composition of

(a) ventral and dorsal roots,

Ventral roots are motor dorsal roots are sensory.

(b) the spinal nerve proper, : both motor and sensory

(c) ventral rami and dorsal rami. both: motor and sensory

Discuss the distribution of the dorsal and ventral rami of spinal nerves.

Dorsal rami supply the posterior body trunk whereas the thicker ventral rami supply the rest of the body trunk and the limbs

Name the four major nerve plexuses, give the major nerves of each, and describe their distribution.

1. Cervical: serves the diaphragm and muscles of shoulder and neck phrenic nerve

2. Brachial: upper limbs• Axillary• Radial• Median• Musculocutaneous • Ulnar

• 3. Lumbar: serve the abdominal region and the anteromedial thigh.• Femoral• Obturator

4. Sacral : supply buttock, posterior thigh, and almost all leg and foot. The sciatic nerve – largest nerve in the body; divides into common fibular

nerve and tibial nerve. Superior and Inferior Glutea

Identify the site of origin and explain the function of the sympathetic and parasympathetic divisions of the autonomic nervous system.

Sympathetic Division = Fight/Flight

Originates from T1 through L2

Ganglia are at the sympathetic trunk (near the spinal cord)Short pre-ganglionic neuron and long post-ganglionic neuron transmit impulse from CNS to the effectorNorepinephrine and epinephrine are neurotransmitters to the effector organs

Parasympathetic division = Take it EasyOriginates from the brain stem and S1 through S4

Terminal ganglia are at the effector organAlways uses acetylcholine as a neurotransmitter

Contrast the effect of the parasympathetic and sympathetic divisions on the following organs: heart, lungs, digestive system, blood vessels

Organ Parasympathetic SympatheticHeart Decrease heart rate Increase heart rateLungs Contracts bronchiole (small air

passage) smooth muscle.Dilates bronchioles.

Digestive System Increases peristalsis and enzyme/mucus secretion.

Decreases glandular and muscular activity.

Blood vessels constricts dilates